Bobby and Tommy shared some erasers in the ratio of 3 : 8. After both each gave away 35 erasers to their brother, the ratio of the number of erasers Bobby had to the total number of erasers left was 1 : 6. How many erasers did the two boys have in the end?

	Bobby	Tommy	Difference
Before	3x4 = 12 u	8x4 = 32 u	5x4 = 20 u
Change	- 35	- 35
After	1x5 = 5 u	5x5 = 25 u	4x5 = 20 u

Number of erasers that Bobby and Tommy each gave to their brother is the same.

The difference in the number of erasers at first and in the end between Bobby and Tommy remains unchanged.  Make the difference in the number of erasers the same.  LCM of 5 and 4 is 20.

Number of erasers that Bobby gave to their brother
= 12 u - 5 u
= 7 u

7 u = 35

1 u = 35 ÷ 7 = 5

Number of erasers that the two boys had in the end
= 5 u + 25 u
= 30 u
= 30 x 5
= 150

Answer(s): 150